Certain Balance Sheet Components



Accounts receivable, net	March 31, 2014		December 31, 2013
	(in thousands)
Trade receivables (net of allowance of $8,758 and $8,368)	$	310,927	$	328,240
Unbilled receivables	30,620		28,469
Total accounts receivable, net	$	341,547	$	356,709

At March 31, 2014 and December 31, 2013, $3.1 million and $3.2 million, respectively, were recorded within trade receivables as billed but not yet paid by customers, in accordance with contract retainage provisions. At March 31, 2014 and December 31, 2013, contract retainage amounts that were unbilled and classified as unbilled receivables were $5.0 million and $4.3 million, respectively. These contract retainage amounts within trade receivables and unbilled receivables are expected to be collected within the following 12 months.

At March 31, 2014, long-term unbilled receivables totaled $4.5 million. These long-term unbilled receivables are classified within other long-term assets, as collection is not anticipated within the following 12 months. We had no long-term billed contract retainage receivables at March 31, 2014, as we expect to collect all contract retainage receivables within the following 12 months. At December 31, 2013, long-term unbilled receivables totaled $4.7 million. These long-term unbilled receivables are classified within other long-term assets. We had no long-term billed contract retainage receivables at December 31, 2013.



Allowance for doubtful account activity	Three Months Ended March 31,
	2014			2013
	(in thousands)
Beginning balance	$	8,368		$	7,372
Provision (release) of doubtful accounts, net	606			(904		)
Accounts written-off	(232		)	(105		)
Effect of change in exchange rates	16			(219		)
Ending balance	$	8,758		$	6,144



Inventories	March 31, 2014		December 31, 2013
	(in thousands)
Materials	$	110,861	$	102,596
Work in process	10,958		13,770
Finished goods	70,754		61,101
Total inventories	$	192,573	$	177,467

Our inventory levels may vary from period to period as a result of our factory scheduling and the timing of contract fulfillments, which may include the buildup of materials in preparation for customer orders or finished goods for shipment.

Consigned inventory is held at third-party locations; however, we retain title to the inventory until it is purchased by the third-party. Consigned inventory, consisting of raw materials and finished goods, was $4.2 million and $6.4 million at March 31, 2014 and December 31, 2013, respectively.



Property, plant, and equipment, net	March 31, 2014			December 31, 2013
	(in thousands)
Machinery and equipment	$	311,578		$	309,525
Computers and software	101,002			99,654
Buildings, furniture, and improvements	146,214			145,926
Land	24,039			24,005
Construction in progress, including purchased equipment	13,393			14,257
Total cost	596,226			593,367
Accumulated depreciation	(358,900		)	(346,547		)
Property, plant, and equipment, net	$	237,326		$	246,820



Depreciation expense	Three Months Ended March 31,
	2014		2013
	(in thousands)
Depreciation expense	$	14,522	$	14,013